Filter for vapor compression systems

ABSTRACT

In a closed loop refrigerant system and method, a refrigerant liquid filter is provided downstream of the condenser to receive and clean high pressure, high temperature liquid refrigerant. The invention provides means for cooling liquid refrigerant so as to render otherwise soluble contaminants insoluble before leaving the filter. The means for cooling preferably includes a refrigerant line provided in thermal contact with the liquid refrigerant in the filter. The refrigerant line contains expanded refrigerant gas or expanded liquid/gas mixture, which is at a lower temperature than the liquid refrigerant received from the condenser. Condensed liquid refrigerant is provided to the filter, which filter further includes a filter element for removing contaminants that have been rendered insoluble by the cooling of the liquid refrigerant. The filtered liquid refrigerant, from which otherwise soluble contaminants and insoluble contaminants have been removed, can then be supplied to downstream components such as expansion devices, evaporators, and compressors.

FIELD OF THE INVENTION

The present invention relates to an improved refrigerant filtration system, and, more particularly, to a system wherein a liquid refrigerant filter is cooled to solidify otherwise soluble contaminants, which are then filtered out from the cooled liquid refrigerant.

BACKGROUND OF THE INVENTION

It is known that contaminants in the refrigerant of a refrigerant system compromise the performance of the system. Contaminants interfere with system efficiency, and can plug or partially block critical system components such as expansion devices, capillary tubes, short tubes, thermostatic expansion valves, and the like. Contaminants such as water and acids may also cause corrosion of system components. Unfortunately, contaminants are an unavoidable by-product of operating a compressor-driven refrigeration system. Contaminants in refrigerant can result from, among other things, leaking compressor oil seals, and thermal or chemical breakdown of system fittings, seals, gaskets, refrigerant, additives, and the like. Contaminants can exist in any of gaseous, liquid, and/or solid forms, depending upon the nature of the contaminant and its location within the refrigeration system. For example, contaminants may change from liquid to solid depending upon the pressure and temperature of refrigerant in any given part of the loop.

To help reduce contaminants, refrigerant purification systems are generally utilized. Exemplary systems are described, for example, in U.S. Pat. Nos. 3,699,781; 4,285,206; 4,364,236; 4,805,416; 4,768,347; 4,809,520; 4,939,903; 5,072,593; 5,245,840; and 5,617,731. However, none of these exemplary systems solve the particularly difficult problem of removing soluble contaminants from liquid refrigerant within the high pressure liquid refrigerant loop within a compressor-driven refrigeration system.

For example, U.S. Pat. No. 5,617,731 (hereinafter the '731 patent”) is directed to refrigerant recovery/recycling apparatus for refrigerant systems. A vapor type filter/dryer is arranged downstream of the compressor inlet which received recovered vapor refrigerant. The vapor filter/dryer is cooled by a heat exchanger in order to lower the solubility of non-condensable gas in liquid refrigerant flowing through the filter/drier. The figures of the '731 patent illustrate that the filter/dryer may have a tube extending from a downstream expansion device around a heat exchanger and also wrapped around the filter/dryer to place the contents of the filter/dryer in thermal contact with the contents of the tube. However, the vapor filter/dryer of the '731 patent does not filter liquid refrigerant, and does not remove precipitated solids. The '731 patent only teaches cooling of a vapor filter/dryer for the purpose of removing non-condensable gas from the refrigerant vapor. The '731 patent therefore does not solve the problem of removing soluble contaminants from liquid refrigerant.

By way of further example, U.S. Pat. No. 4,939,903 (hereinafter “the '903 patent”) is directed to an apparatus and method for recovering and purifying refrigerant, wherein the refrigerant is routed through expansion means into the internal coil of a purification unit, causing the coil to cool. The refrigerant exits the coil, and subsequently is passed back into the internal chamber of the purification unit in its expanded gaseous state, where impurities are condensed onto the cool coil. The apparatus disclosed in the '903 patent therefore provides for cooling of vapor refrigerant to cause condensed impurities to solidify on the coil. The apparatus of the '903 patent is not a liquid refrigerant filter, and does not include a filter element. The '903 patent therefore does not solve the problem of removing soluble contaminants from liquid refrigerant.

Therefore, a shortcoming of known refrigerant filter systems is that they do not remove the contaminants such as particles, moisture and acid that are soluble in the liquid refrigerant at the elevated temperatures typically experienced in the high-pressure side of a refrigerant loop.

SUMMARY OF THE INVENTION

A refrigeration system is provided that circulates a refrigerant through a closed loop having a high pressure side extending from a compressor, through a condenser, to a flow-restricting expansion device, and a low pressure side extending between the expansion device, through an evaporator, to the compressor. The system further includes a liquid refrigerant filter disposed in the high pressure side of the closed loop, the filter in one example communicably connecting the condenser and a flow-restricting expansion device, and also including a filter element for removing solid and semi-solid contaminants. The system further includes a system for cooling liquid refrigerant received by the filter, wherein the system for cooling liquid refrigerant lowers the temperature of the received refrigerant by an amount sufficient to render an otherwise soluble contaminant insoluble, and wherein the insoluble contaminant is captured by the filter element. Preferably, the system for cooling liquid refrigerant comprises a refrigerant line containing expanded refrigerant sourced from the closed loop downstream of the expansion device.

The invention further provides methods of removing soluble contaminants from liquid refrigerant in the high pressure side of a closed loop refrigeration system. In one example, the methods include the step of providing a liquid refrigerant filter in the high-pressure side of the closed loop, the filter communicably connecting the condenser and a flow-restricting expansion device, the filter including a filter element for removing solid and semi-solid contaminants. The method further includes the step of providing a liquid refrigerant cooling system for cooling liquid refrigerant received by the filter, and operating the cooling system so as to lower the temperature of the received refrigerant by an amount sufficient to render an otherwise soluble contaminant insoluble.

The invention further provides a liquid refrigerant filter assembly. In one example, the filter assembly includes a primary chamber configured for communicable connection to the condenser of a refrigeration system to receive liquid from the condenser, the primary chamber housing a filter element, the primary chamber defined by a first sidewall that separates the primary chamber from a secondary chamber, the first sidewall including an exit passageway disposed and configured for conveying received liquid refrigerant to an expansion device located within the secondary chamber. The secondary chamber is defined by a second sidewall, the secondary chamber being configured to place expanded refrigerant from the expansion device in thermal contact with the first sidewall, the second sidewall further configured and disposed to permit connection to a downstream component of a refrigerant loop.

One advantage of the present invention is that it eliminates otherwise soluble contaminants in the high pressure liquid refrigerant before passage of the liquid refrigerant through the remainder of the refrigeration system.

Another advantage of the present invention is that it cools and removes, such as by adsorption or absorption, substantially all otherwise soluble contaminants in the liquid refrigerant received from the condenser in a very simple and reliable manner, in an isenthalpic manner that does not adversely affect energy efficiency of the system.

Still another advantage of the present invention is that it achieves a continuous range of filtering conditions so as to quickly clean the refrigerant by precipitating and removing solid and semi-solid contaminants from the liquid refrigerant.

Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an embodiment of a refrigerant system of the present invention, including a liquid refrigerant filter of the present invention.

FIG. 2 is a cross-sectional view of a first embodiment of the filter of FIG. 1 in accordance with the present invention.

FIG. 3 is a cross-sectional view of a second embodiment of a liquid refrigerant filter in accordance with the present invention.

FIG. 4 is a cross-sectional view of a third embodiment of a liquid refrigerant filter in accordance with the present invention.

Whenever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a closed loop refrigerant system 100 employing a liquid refrigerant filter of the present invention in a first embodiment. As shown in FIG. 1, the high-pressure side of the refrigerant loop includes a compressor 10 that is provided to compress refrigerant vapor. The high-pressure compressed refrigerant vapor is conveyed to a condenser 12 within the high-pressure side of the refrigerant loop. The condensed liquid refrigerant from the condenser 12 is then conveyed to a filter 14, also located within the high-pressure side of the refrigerant loop.

As shown in FIGS. 2-4, the filter 14 is an in-line filter that includes a filter element 30 selected to permit adequate flow of liquid refrigerant from the filter 14 to a downstream expansion device 16, while effectively removing any solid or semi-solid contaminants. The filter element 30 preferably also includes a drying element for removing water and moisture from the liquid refrigerant.

The system 100 further includes a system to cool the liquid refrigerant to solidify otherwise soluble contaminants, which solidified contaminants are then captured, or adsorbed by, the filter element 30 of the filter 14. For example, in the first embodiment of the system 100 shown in FIGS. 1-2, the system for cooling the filter 14 includes a refrigerant coil 18 containing expanded refrigerant sourced from downstream of the expansion device 16. Thus, the refrigerant in the refrigerant coil 18 is cooler than the liquid refrigerant flowing into the filter 14 from the condenser 12. The refrigerant coil 18 is in thermal contact with the liquid refrigerant flowing through the filter 14 from the condenser 12, thereby cooling the liquid refrigerant in the filter 14. The amount of cooling provided by the refrigerant coil 18 to the refrigerant liquid within the filter 14 is sufficient to cause contaminants in the refrigerant liquid to precipitate out of solution and be captured by the filter element of the filter 14. For example, the amount of cooling may be determined by the liquidus-solidus transition temperature, or by a solubility index, for a known contaminant in a selected high temperature/high pressure liquid refrigerant. For example, the refrigerant may be any known refrigerant, but is preferably R-134a, R-407C, R410A, and combinations thereof. The contaminant to be removed can be any known contaminant, but is preferably selected from water, acids, inorganic chlorides, inorganic fluorides, dirt, water, sludge, wax, clathrate hydrates, and combinations thereof. The amount of cooling accomplished to precipitate contaminants can be adjusted by varying various parameters such as the volume of the filter 14, the filter flow rate, the volume and flow rates in the refrigerant coil 18, thermal efficiency of the thermal contact between the coil 18 and the filter 14, the selection of refrigerant, and combinations thereof.

In the system of FIG. 1, throttled refrigerant is passed a coil 18 to cool the liquid refrigerant contents of the filter 14, thereby aiding in the precipitation and removal of otherwise soluble contaminants from the liquid refrigerant. The amount of cooling accomplished to precipitate contaminants can be adjusted by varying various parameters such as the volume of the filter 14 filter flow rate, volume and flow rate in the refrigerant coil 18, thermal efficiency of the thermal contact between the coil 18 and the filter 14, and the selection of refrigerant, and combinations thereof.

As shown in FIG. 2, in a first embodiment, the filter 14 includes a primary chamber 22 surrounded by a sidewall 15 that forms an outer housing of the filter. The primary chamber is communicably connected to an upstream condenser 12 and to a downstream expansion device 16. In this embodiment, a refrigerant coil 18 is communicably connected to the outlet of the expansion device 16. The refrigerant coil 18 is disposed in contact with, or in close proximity to the outside of the sidewall 15 so as to render thermal contact between the expanded refrigerant in the coil 18 and the liquid refrigerant in the primary chamber 22 of the filter 14.

In a second embodiment shown in FIG. 3, the system for cooling the refrigerant liquid in the filter 14 includes a filter 14 and expansion device 16 combined within a single unit. As shown in FIG. 3, the filter 14 includes a primary chamber 22 that is communicably connected to the high-pressure liquid refrigerant line from the condenser 12 for receiving high-pressure liquid refrigerant. The primary chamber 22 includes a filter element 30 for capturing solid and semi-solid contaminants. The primary chamber 22 includes a sidewall 23 that separates the primary chamber from a secondary chamber 26. The sidewall 23 is impermeable to gas and liquid, but includes an exit passageway 24 that permits filtered liquid refrigerant to pass to an expansion device 16 contained within the filter 14. Refrigerant passing through the expansion device 16 flashes to yield cooled refrigerant gas and liquid. The cooled refrigerant gas and liquid circulates within the secondary chamber 26, and is contained within the filter 14 by the filter sidewall 15. Because the sidewall 23 is comprised of material that permits thermal transfer, thermal transfer occurs between high-pressure liquid refrigerant in the primary chamber 22 and expanded liquid-gaseous refrigerant in the secondary chamber 26. In other words, circulation of expanded refrigerant gas and liquid with the secondary chamber 26 cools the sidewall 23 of the primary chamber 22, thereby cooling hot refrigerant gas within the chamber 22. As previously described, cooling of the hot liquid refrigerant within the primary chamber 22 causes otherwise soluble contaminants to precipitate out of the refrigerant as solids or semi-solids, which are then captured by the filter element 30. The filter sidewall 15 further includes a communicable connection 28 to permit the expanded refrigerant to pass to downstream components such as additional expansion devices, the evaporator 20, and eventually to the compressor 10. The filter 14 may optionally further include features to promote desired thermal transfer by efficient circulation of the expanded refrigerant within the secondary chamber 26. For example, as shown in FIG. 3, one or more baffles 32 may be provided to deflect and redirect expanded gas leaving the expansion device 16 so that the refrigerant circulates before escaping through connection 28.

In an alternative embodiment of the filter shown in FIG. 4, the expansion device 16 is connected to a refrigerant line 18 that is coiled throughout the secondary chamber 26 in close proximity to the sidewall 23 of the primary chamber 22. In this alternative embodiment, the coil 18 is contained by the sidewall 15 of the filter 14, save for a communicable connection 28 through the sidewall 15 that permits the coil 18 to be connected to downstream components such as the evaporator 20.

The filter 14 in one example filters and removes both insoluble contaminants such as dirt, as well as otherwise soluble contaminants from the hot liquid refrigerant received from the condenser, and preferably as early as possible before the contaminates can reach the expansion device 16 of the system 100. Known liquid refrigerant filter elements 30 can be provided in combination with the means for cooling the refrigerant liquid, thereby removing insoluble as well as otherwise soluble contaminants precipitated by the cooling process previously described herein.

Optionally, pressure gauges are provided both upstream and downstream of the filter 14, respectively, to provide a continuous indication of the pressure drop across the filter 14. Providing such pressure gauges may assist in determining when a new filter element 30 is required, thereby avoiding a clogged filter 14 that would compromise system performance.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A refrigeration system comprising: a refrigerant loop comprising a high pressure side and a low pressure side, the high pressure side extending from an outlet of a compressor through a condenser to an expansion device, the low pressure side extending between the expansion device through an evaporator to an intake of the compressor; a liquid refrigerant filter disposed in the high pressure side of the loop and communicably connecting the condenser and the flow-restricting expansion device, the filter comprising a filter element for removing solid and semi-solid contaminants; and a liquid refrigerant cooling system to cool refrigerant received by the filter, the liquid refrigerant cooling system being configured and disposed to lower the temperature of the received refrigerant in the filter by an amount sufficient to render an otherwise soluble contaminant in the received refrigerant insoluble, and wherein the insoluble contaminant is captured by the filter element.
 2. The refrigeration system of claim 1, wherein the liquid refrigerant cooling system comprises a refrigerant line being configured to circulate expanded refrigerant sourced from the closed loop downstream of the expansion device.
 3. The refrigerant system of claim 2, wherein the filter comprises a housing defined by a sidewall, and wherein the refrigerant line is outside of the housing.
 4. The refrigerant system of claim 3, wherein the housing is substantially cylindrical, and the refrigerant line comprises a coil wrapped in a spiral configuration around the housing.
 5. The refrigerant system of claim 1, wherein the filter and the liquid refrigerant cooling system are contained within a common insulated housing.
 6. The refrigerant system of claim 1, wherein the filter comprises: a primary chamber communicably connected to the condenser, the primary chamber housing the filter element, the primary chamber defined by a first sidewall that separates the primary chamber from a secondary chamber, the first sidewall including an exit passageway for conveying liquid refrigerant to an expansion device located within the secondary chamber; wherein the secondary chamber is defined by a second sidewall, the secondary chamber being configured to place expanded refrigerant from the expansion device in thermal contact with the first sidewall, the second sidewall further including a communicable connection to permit expanded refrigerant to flow to a downstream component of the refrigerant loop.
 7. The refrigerant system of claim 6, wherein the secondary chamber includes a baffle disposed to direct expanded refrigerant toward the first sidewall.
 8. The refrigerant system of claim 7, wherein the baffle is positioned adjacent an open end of the expansion device.
 9. The refrigerant system of claim 8, wherein the baffle is positioned between the open end of the expansion device and the communicable connection of the second sidewall, wherein refrigerant leaving the open end of the expansion device is redirected away from the communicable connection by the baffle to place the refrigerant in thermal contact with the first sidewall before exiting the secondary chamber via the communicable connection of the second sidewall.
 10. The refrigerant system of claim 6, wherein the filter further comprises an insulated outer housing surrounding the second sidewall.
 11. The refrigerant system of claim 6, wherein the first sidewall is substantially cylindrical.
 12. The refrigerant system of claim 6, wherein the secondary chamber includes a refrigerant line in thermal contact with the first sidewall.
 13. The refrigerant system of claim 12, wherein the first sidewall is substantially cylindrical.
 14. The refrigerant system of claim 13, wherein the refrigerant line is a coil wrapped in a spiral configuration around the first sidewall.
 15. The refrigerant system of claim 12, wherein the filter further comprises an insulated outer housing surrounding the second sidewall.
 16. A method of removing soluble contaminants from liquid refrigerant in the high pressure side of a closed loop refrigeration system, the method comprising the steps of: providing a liquid refrigerant filter in the high-pressure side of the closed loop, the filter communicably connecting the condenser and a flow-restricting expansion device, the filter comprising a filter element for removing solid and semi-solid contaminants; receiving liquid refrigerant into the filter; conveying liquid refrigerant from the filter to an expansion device; circulating expanded refrigerant from the expansion device around a housing of the filter; cooling liquid refrigerant in the filter by the circulation of refrigerant from the expansion device by an amount sufficient to render an otherwise soluble contaminant in the received liquid refrigerant insoluble; and removing the contaminant using the filter element.
 17. The method of claim 18, further comprising the step of conveying the filtered liquid refrigerant to a downstream component in the closed loop refrigeration system.
 18. The method of claim 19, wherein the step of cooling refrigerant includes circulating refrigerant from the expansion device through a coil wrapped in a spiral configuration around the filter.
 19. A filter for a refrigerant system, the filter comprising: a primary chamber configured for communicable connection to the condenser of a refrigeration system to receive liquid from the condenser, the primary chamber housing a filter element, the primary chamber defined by a first sidewall that separates the primary chamber from a secondary chamber, the first sidewall including an exit passageway disposed and configured for conveying received liquid refrigerant to an expansion device located within the secondary chamber; wherein the secondary chamber is defined by a second sidewall, the secondary chamber being configured to place expanded refrigerant from the expansion device in thermal contact with the first sidewall, the second sidewall further configured and disposed to permit connection to a downstream component of a refrigerant loop.
 20. The filter of claim 19, wherein the secondary chamber includes a refrigerant line in communication with the expansion device and in thermal contact with the first sidewall. 